; Here is an IDL program to plot the sigma levels for the 2km L. Michigan grid:
 
z=[0.00000, -0.012500, -0.025000, -0.037500, -0.050000, -0.062500, -0.075000,$
-0.087500, -0.100000, -0.112500, -0.125000, -0.137500, -0.150000, -0.162500,$
-0.175000, -0.187500, -0.200000, -0.212500, -0.225000, -0.237500, -0.250000,$
-0.265407, -0.284398, -0.307805, -0.336656, -0.372217, -0.416049, -0.470075,$
-0.536667, -0.618745, -0.700824, -0.767415, -0.821441, -0.865273, -0.900835,$
-0.929686, -0.953093, -0.972083, -0.987500, -1.000000]

n=n_elements(z)
print,n
plot,[0,1],[-1,0],/nodata
for i=0,n-1 do plots,[0.4,0.6],[z(i),z(i)]
a=findgen(16)*!pi/8.
usersym,cos(a),sin(a)
for i=0,n-2 do plots,0.5,0.5*(z(i)+z(i+1)),psym=8,symsize=0.3
end